Hitachi carb ?'s / issues [stock 2 barrel]

[Pacific coast Datsun]

Ok carb in question is a stock 2 barrel Hitachi carb thats on my boat. Motor is a L 20 & is stock as well. My issues are these....

1. Its using way more gas than it should...[ran it 30 minutes & used 1/4 tank]

2. & it's running rich...[black soot on the rear of the boat]

Im comparing mine to Steroids boat [same motor & running a 32/36 Weber]

Our gas tanks are the same size & he get much better mileage compared to me.

Im looking to set it back to baseline settings & see if that makes a difference. Can someone post a link & or a "how to" so i can adjust it.

Or should i just have it rebuilt & call it good ?

It has new plugs cap & rotor & the dist. is a matchbox.

I adjusted the valves as well back to factory specs. She fires right up & idle's just fine.

I could swap on my 32/36 thats on my 620 but i'd like to leave the L 20 stock.

Any help is appreciated :cool:

[datzenmike]

Running rich could be the choke not turning off or the float is sticking and the carb overfilling and flooding.

 

When warmed up look at the choke plate, it should be fully open. The front of the carb has a small round glass bull's eye sight glass with a dot etched in the middle. The fuel level should be even with or close to the dot fro proper filling.

[68Datsun510]

Choke opening fully?

[68Datsun510]

Mike sniped it first :P

[datzenmike]

Primary and secondary jets could have been accidentally swapped while rebuilding.

 

Mike sniped it first :P

 

... rust never sleeps.

[68Datsun510]

"Primary and secondary jets could have been accidentally swapped while rebuilding."

 

Im guilty of this with my weber. Re-check this!

[Pacific coast Datsun]

Running rich could be the choke not turning off or the float is sticking and the carb overfilling and flooding.

 

When warmed up look at the choke plate, it should be fully open. The front of the carb has a small round glass bull's eye sight glass with a dot etched in the middle. The fuel level should be even with or close to the dot fro proper filling.

Thanks D-mike. It has an electric choke thats not wired up. Not sure if this is an issue living in this hot climate. Can i simply remove the choke altogether & / or wire it to the "fully open" position ?

& from what ive seen the fuel level goes halfway up the sight glass when shes running. Ill have a look for the etched dot & compare.

[Spades]

Thanks D-mike. It has an electric choke thats not wired up. Not sure if this is an issue living in this hot climate. Can i simply remove the choke altogether & / or wire it to the "fully open" position ?

& from what ive seen the fuel level goes halfway up the sight glass when shes running. Ill have a look for the etched dot & compare.

 

I have never worked on a Hitachi carburetor before, but most electric chokes use current passing through a bi-metal compound to warm the coil up and cause the choke to open...meaning that when the car is set to the "run" position on your ignition switch, current starts running through the electric choke and then as the bi-metal coil heats up, it opens the choke. Most electric chokes can be "opened" by stabbing the throttle, or by not pressing the throttle (prior to ignition) to engage the choke, but if your choke is sticking and is not wired up or was improperly installed, it could be staying closed creating a rich condition.

 

With that being said, you can expect that you should see loss in performance from the rich condition, also, a stuck choke limits incoming air, which means the motor will fall on its face or run poorly, especially in warm conditions. The jets may have been swapped, a float may be stuck, or it could be any number of things. You should be able to answer some of those questions though by taking off the air filter and looking into the carb(don't do this if it is backfiring, it is a great way to loose eyebrows). If the float is stuck, you should see fuel droplets dripping on the inside of the carb from whatever side the float bowl is on. You may also be able to see the choke plate and see if it is stuck closed. You can also make sure the butterflies are opening properly, and may even be able to see if there is a ton of fuel gushing from the primary jet.

 

I suppose the best place to start is to see how it runs, check the carburetor, and then make sure there isn't anything else ignition related that could be causing this (such as timing not set properly creating low power, unburnt fuel in the form of black soot, and bad gas mileage). I would look at your carburetor and then make sure your timing is not retarded, and then go from there. Have you pulled a plug to see what it looks like? Let us know what you find.

[Pacific coast Datsun]

Great advice thanks. I pulled the plugs when i did the valves & they are all very clean & probably recently replaced. Ill have to check the timing & see if thats off too. There are 2 wires coming off the choke & Im wondering where they connect. This is on a boat w/ a very simple wire harness & if hooking up the choke will possibly cure the black soot / running rich issue then ill do it. Im also noticing that after a few days of sitting the gas will drain back into the tank. Ive read that could be a bad float or bad sight glass gasket. Im half tempted to put my 32/36 manual choke on & then compare gas useage.